Dual 50 Troublshooting

[purpletele]

The Dual 50 sounds really nice.  I modified a few components as suggested and I really like the way the JCM 800 sounds.

I ran into an issue after about 1/2 hour of playing.  Here are the symptoms and results.

Looking for any ideas:

1.  Playing really well and enjoying it.
2.  Lost sound.
3.  Visually I see only one EL34 burning
4.  I figured that is not unusual since I hammered the tubes during the initial startup.
5.  When I pulled the chassis I noticed that I fried the two 1K 3 Watt Grid resistors.
6.  That answered my question as to whether the resistor should be 5Watts or 3 Watts.
7.  I changed the resistor to a 1K 5Watt.
8.  I changed the tubes, changed the HT fuse which was burned,
9.  Plate voltage was 493 so I set the bias to 36.8 mV
10.  Up and running and sounding really chimey with my Tele.
11.  I left the amp running and came back 10 minutes later and the sound was gone and the HT fuse had fried again.

12. I just found one of the bias caps blown apart.  Not sure if that happed originally or after I replaced the 3 watt grid resistors.

Any ideas of what could create the current overload?

Thanks
BV

[sluckey]

May not really be a current overload. Maybe try a SloBlo fuse.

Try this... Remove the fuse and tack solder a 1Ω resistor across the fuse holder. Now connect your meter across the fuse holder, set to measure DC milliVolts. The mV will be the equivalent of the dc current in mA that is flowing through the 1Ω resistor. What do you have with the amp just idling?

[purpletele]

May not really be a current overload. Maybe try a SloBlo fuse.

Try this... Remove the fuse and tack solder a 1Ω resistor across the fuse holder. Now connect your meter across the fuse holder, set to measure DC milliVolts. The mV will be the equivalent of the dc current in mA that is flowing through the 1Ω resistor. What do you have with the amp just idling?

Thanks Steve,  I had just edited my post.  I had found a bias cap blown out, all I have is a 10 uF 160V, so I may out of luck for a few days.

Not sure if I blew out the cap originally or after I replaced the resistors, Had to be after the resistors because it played really nice.

[purpletele]

Update

Found a new 10 uF cap 100v.

1. Replaced the cap
2. Replaced the fuse with a Slo-Blo
3. New Plate Voltage of 495
4. Set the bias at 35.8

5. The amp is back to being real chimey with the Tele and that is good news.

6. I'll watch it and let it burn in today.
7. Might have been a Leminy Snicket series of perfect events starting with the grid resistors.  Not sure.

Cool amp!!